A watch case typically comprises four main components: a middle, a crystal, a bezel surrounding the crystal fitted on top of the middle, and a back fitted underneath the middle. The bezel and the middle may in some cases be formed as a single piece, and the middle also typically includes two pairs of projecting lugs that enable the case to be attached to a watch strap or bracelet. The case middle surrounds the watch movement. It is typically made from solid metal material, and the middle is generally the most massive of the watch case components by far.
In order to reduce the amount of material used in a watch case and hence also the weight of the case and the cost of the material used to produce it (particularly in the case of precious metals), it has been proposed to hollow out the middle. For example, EP626625 describes a precious metal watch case in which the middle is formed by fitting a central cylindrical part and an annular peripheral part together so that an annular cavity exists between the two. In order to improve the strength of the middle, a support frame in a non-precious metal is placed within the cavity.
Similarly, in CH664251, a unitary bezel-middle having its inner wall hollowed-out is fitted together with and fixes in place a separate L-shaped encasing piece that itself holds the watch movement. A hollow cavity exists between the bezel-middle and the encasing piece.
Unfortunately, such prior art solutions for producing hollowed-out watch case middles generally result in watch cases that are of significantly reduced strength and that require complex assembly. In addition, because the middle is not unitarily formed, the watch case may suffer from reduced sealing or watertightness compared to a conventional watch case. Furthermore, where a massive middle is initially produced and then subsequently hollowed-out, there may be a significant amount of material wasted that cannot be readily reused.
There is consequently a need to provide a reduced weight watch case and in particular a watch case middle for which the above-mentioned shortcomings are alleviated.